The present invention is related to a retractor reel for vehicle safety belts, and particularly for safety belts in motor cars, of the type in which the belt is automatically wound onto a shaft rotatably supported by at least one bearing at each end, when the belt is not used, the bearings being positioned in opposite walls of a support carrying the safety belt. The retractor reel device comprises a first locking means and a second locking means to co-operate and engage with the first locking means. One of the locking means is attached to the support and the other is attached to the rotatable shaft. One of the locking means is movable and arranged to be moved between an idle position, in which the locking means does not engage with the other locking means, and an operative position, in which the locking means engages with the other locking means for locking the shaft.
Retractor reels of the type set forth above are known. These prior art devices have been provided with locking means either only at one end or at both ends of the rotatable shaft. In the first case, with a single-ended locking of the rotatable shaft the locking means are lighter and more accurate in operation, so that the desired limit values for the on and off operation of the locking means can be achieved with a comparatively high accuracy. On the other hand, the strength of the construction is low, because the support is unevenly loaded when a heavy load occurs on the strap of the safety belt, so that the support may be deformed and there is a risk that the shaft may slip out of its bearings, thus releasing the belt as opposed to locking it. Therefore, the parts of the support forming the locking device must be comparatively generously proportioned to be able to take up the loads that arise without any risk of deformation. In the second case, with a double-ended locking of the rotatable shaft the locking means are heavier and more difficult to guide to an accurate operation. Therefore, it is frequently difficult to achieve the desired operation at the desired limit values with these devices. However, in these constructions a more even loading of the support is obtained, so that the necessary strength can be obtained with a weaker design ofthe support parts.
Furthermore, it is previously known, for example from British Patent Specification No. 2,026,305, to use two bearings at each end of the rotatable shaft, one bearing consisting of two bearing means having a low friction and a comparatively low strength and the other bearing consisting of two bearing means having a high strength but lacking the precision necessary for a silent running and a low friction. The first bearing is in operation in normal running and provides a silent running and a low friction during extraction and retraction of the strap. The second bearing is used only in case of a very high loading of the safety belt, for example in a collision, and will take up forces that arise, because the first bearing will yield in such a case. In this prior art design a double-ended locking is used.
It is also previously known, for example from Swedish Patent Application No. 7711192-0, to mount the rotatable shaft on pivoted arms, so that the shaft when loaded can be moved to engagement with fixed locking means for locking the shaft. In this case, however, the complete shaft must be mounted movably in the support which makes the construction complicated and expensive.